This invention relates to the field of friction clutches having automatic adjustment features, and more particularly to friction clutch automatic adjustment features employing a spring ferrule to retain one end of an adjustment spring.
Known friction clutches provide a releasable torsional connection between a motor vehicle engine flywheel and an associated transmission. Repeated clutch disengagement and engagement cycles wear the friction material of the clutch driven disc. As the friction material wears, the clutch clamping load generated by a spring acting directly or indirectly against the pressure plate tends to decrease. Clutches are commonly provided with adjustment mechanisms to compensate for wear of the friction material and the attendant loss of clamping load. Cam elements and helical threads are two alternative devices employed as adjusting mechanisms. Relative rotation between the cam elements or between the threaded elements produces an axial displacement which compensates for the wear of the friction material. A spring or springs are used to induce the necessary relative rotation. One known cam adjustment mechanism employs a coil type tension spring. The spring has a working portion of a first coil diameter, and end portions of a second coil diameter disposed at each end of the working portion. The second coil diameter is significantly smaller than the first coil diameter. At the extreme ends of the end portions are flare portions which taper, in a relatively short axial distance, to an end coil of approximately the same coil diameter as the working portion. The flared portion on a first end is connected to the rotatable cam for movement therewith. The flared portion on the second end engages the clutch cover through a spring ferrule mounted to a bracket as shown in FIG. 3. The use of a bracket is disadvantageous in at least two regards. First, the inclusion of the bracket adds cost, assembly complexity and a potential source of noise to the clutch assembly. Second, it requires that there be a break or a gap in the circumferential dust baffle. The dust baffle is disposed radially inwardly of the cams and protects the cams from dirt and grease thrown radially outwardly by the rotating clutch. The gap necessitated by the bracket compromises the effectiveness of the baffle.
It is desired to provide a spring ferrule which can be mounted to the clutch cover without the use of a bracket.
A cover assembly for a friction clutch for a motor vehicle includes a cover and a ferrule. The cover has a ferrule aperture passing therethrough from an outer side to an inner side. The ferrule is a one piece unitary structure and is disposed in the ferrule aperture. The ferrule has a spring receiving portion and a base portion and an axis of orientation passing through both the spring receiving portion and the base portion. The spring receiving portion projects from the ferrule aperture beyond the inner side. The spring receiving portion has a spring aperture. The base portion has a pilot portion disposed within the ferrule aperture. The pilot portion is of a size complementary to the ferrule aperture. The size of the pilot portion is selected to enable the ferrule to be positively positioned within the ferrule aperture. The base portion also has a travel limit portion extending radially beyond the ferrule aperture and engaging the outer side of the cover to prevent the base portion from passing through the cover.
A friction clutch for a motor vehicle includes a cover, a pressure plate, a biasing member, an adjustment mechanism, a tension coil spring, and a spring ferrule. The cover has an axis of rotation, and also has an inner side and an outer side opposite the inner side. The cover has a ferrule aperture passing therethrough from the outer side to the inner side. The pressure plate is coupled to the cover for rotation therewith about the axis and disposed on the inner side of the cover. The biasing member is interposed between the cover and the pressure plate and biases the pressure plate toward an engaged pressure plate position. The adjustment mechanism is centered about the axis and is operably disposed between the cover and the biasing member. The tension coil spring is part of the adjustment mechanism and has an end feature. The spring ferrule is fixedly disposed in the ferrule aperture. The ferrule is a one piece unitary structure. The ferrule has a spring receiving portion and a base portion and an axis of orientation passing through both the spring receiving portion and the base portion. The spring receiving portion projects from the ferrule aperture beyond the inner side. The spring receiving portion has a spring aperture receiving the end feature of the spring. The base portion has a pilot portion disposed within the ferrule aperture. The pilot portion is of a size complementary to the ferrule aperture. The size of the pilot portion is selected to enable the ferrule to be positively positioned within the ferrule aperture. The base portion also has a travel limit portion extending radially beyond the ferrule aperture and engaging the outer side of the cover to prevent the base portion from passing through the cover.
The disclosed spring ferrule can be mounted to a clutch cover without the use of a bracket.
The disclosed clutch cover accommodates the retention of a spring ferrule without the use of a bracket.